The purpose of this study is to evaluate various dibenzodioxins with regard to the following parameters (1) dose response; (2) lethal dose; (3) clinical signs; (4) clinical pathology; and (5) anatomic pathology in guinea pigs and mice. BIBLIOGRAPHIC REFERENCES: McConnell, E.E. and Moore, J.A.: The Comparative Toxicity of Chlorinated Dibenzo-p-dioxin Isomers in Mice and Guinea Pigs. Toxicol. Appl. Pharmacol. (Abstract) 37: 146, 1976. McConnell, E.E., and Moore, J.A.: The Toxicopathology of TCDD. Proceed. Workshop on TCDD, Milan, Italy, October 23-24, 1976 (In press).